The present invention relates to an image recording apparatus which is suitably used for a video camera and the like, and has a recording medium for recording image data such as moving images, still images, and the like (e.g., a solid-state magnetic disk memory, magnetooptical disk memory, optical disk memory, and the like).
As an image recording/reproduction apparatus which records an image and reproduces the recorded image, a video tape recorder that records an analog image signal on a magnetic tape is known. Contrary to such analog image recording/reproduction apparatus, a digital VTR that converts an image signal into a digital signal, and records the digital signal on a magnetic tape, a disk memory that records a digital signal on a solid-state disk or magnetooptical disk, a solid-state memory video that records a digital signal on a solid-state memory such as a flash memory, SRAM, or the like, and the like have been proposed. Such video recording systems compress an input digital signal to reduce the information volume, and can record a large amount of moving image information and still image information with a small storage capacity.
Various compression methods for the image recording apparatus are available. For example, in a method using orthogonal transformation, an image is segmented into a plurality of blocks each having n pixels in the horizontal directionxc3x97n pixels in the vertical direction, the orthogonal transform such as the discrete cosine transform (DCT) or the like is calculated in units of blocks, and each coefficient is rounded to a predetermined number of bits, thus quantizing the image. Since image information is offset to the lower-frequency range, the data volume can be reduced by decreasing the number of bits for high-frequency components. In variable length coding such as Huffman coding or the like, efficient data compression is attained by assigning shorter codes to bit sequences with higher probabilities of occurrence.
Upon compressing a moving image, the difference between neighboring frames is extracted by using a strong correlation between neighboring frames as a nature of moving images, thus greatly compressing the image.
Various moving image recording systems have been proposed. In such system, a moving image is compressed by combining various compression techniques mentioned above to reduce its data volume, and the compressed image data is recorded on a solid-state magnetic disk memory, optical disk memory, or the like.
When recording and deletion of image data onto and from a recording medium are repeated several times, vacant spaces from which data have been deleted and spaces of effective image data which remain undeleted respectively get fragmented in the recording medium, and the number of broad (long) spaces that can continuously record image data becomes small. As a result, since new image data is recorded on distributed small regions, the time required for seek or access on the recording medium is prolonged, thus disturbing high-speed data I/O. Especially since the moving image recording system has a large moving image data volume per unit time, I/Os with the disk memory must be done as fast as possible. For this reason, an increase in time required for seek or access poses a serious problem.
The present invention has been made to solve the above-mentioned problems, and has as its object to provide an image recording apparatus and method that can always assure a continuous recording space of image data on a recording medium.
It is another object of the present invention to provide an image recording apparatus and method which can appropriately determine the re-allocating timing.
It is still another object of the present invention to provide a recording apparatus and method, which can prevent image data blocks from being randomly scattered onto a recording medium upon recording a new image file.
Further objects, features and advantages of the present invention will become apparent from the following detailed description of embodiments of the present invention with reference to the accompanying drawings.